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arXiv · 1003.1106

Zeeman Relaxation of Cold Atomic Iron and Nickel in Collisions with 3He

Cort Johnson·Bonna Newman·Nathan Brahms·John M. Doyle·Daniel Kleppner·Thomas J. Greytak
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Abstract

We have measured the ratio of the diffusion cross-section to the angular momentum reorientation cross-section in the colliding Fe-3He and Ni-3He systems. Nickel (Ni) and iron (Fe) atoms are introduced via laser ablation into a cryogenically cooled experimental cell containing cold (< 1 K) 3He buffer gas. Elastic collisions rapidly cool the translational temperature of the ablated atoms to the helium temperature. The cross-section ratio is extracted by measuring the decays of the atomic Zeeman sublevels. For our experimental conditions, thermal energy is comparable to the Zeeman splitting. As a result, thermal excitations between Zeeman sublevels significantly impact the observed decay. To determine the cross-section ratio accurately, we introduce a model of Zeeman state dynamics that includes thermal excitations. We find the cross-section ratio for Ni-3He = 5 x 10^3 and Fe-3He <= 3 x 10^3 at 0.75 K in a 0.8 T magnetic field. These measurements are interpreted in the context of submerged shell suppression of spin relaxation as studied previously in transition metals and rare earth atoms.

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Cort Johnson, Bonna Newman, Nathan Brahms, John M. Doyle, Daniel Kleppner, Thomas J. Greytak. 2010-03-04. Zeeman Relaxation of Cold Atomic Iron and Nickel in Collisions with 3He. https://doi.org/10.1103/physreva.81.062706

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